1) Considering how new your team is, I would play Base offense and Man to man a couple of games at least. This would let you get a feel for what your team does well and what it's doing poorly.
2) If I'm reading this right, your best player is your PG, but you want him to defend the opponents SG. Easily done, choose him to play at PG. Just above the send orders button you can set your PG to play defense as SG. Remember to change the SG to play defense as PG.
3) M.V.P. is the limit to which the player can be trained. Relatively few if any players have actually hit their cap with MVP potential, but lower potential players quite often will. Basically when a player gets trained to his potential limit, he'll start training very slowly. Read the Game Manual entry for potential
http://www.buzzerbeater.com/community/rules.aspx?nav=Nome... for more information on that.
4) Typically yes, but C and PF have similar needs and you'll want a strong rebounder at PF as well.
Best of luck!